Apple can't predict how your code/app will perform against their APIs, that's your job as a dev and why it's called 'development'. Testing & discovery is all part of the process and why betas are made available.
Dev-woke includes but is not limited to:
- reading the beta and release notes, keeping in mind things are far too fluid for them to be anything more than reference
- checking headers/comments in each API you rely on
- test/test/test - See: Testing Your App on Beta OS Releases
- understanding the difference between warnings and errors and what your reaction should be in both cases
- understanding the specific short and long term impacts of deprecations on -your- code
- scan the forums/internet for what others are doing/seeing
- file bugs to see what comes back
- as applies, use support tickets w/DTS if you get stuck, being sure to have a (non-beta dependant) project that demos your issue
Good on you for checking headers. Be careful out there.
It seems a bit unedifying to me that there is not even a document that is explaining the breaking changes of a new release, but given the complexity of the matter I guess such a document would be almost impossible to write.